"We don't have good observations for how the universe is expanding again so rapidly after a long period of slowing down," Hawking said, addressing a packed audience at Oakland's Paramount Theater, where he delivered a lecture called "Origin of the Universe."
"We cannot be sure of the future of the universe: Is inflation the law of nature? Or will the universe eventually collapse again?" he said.
Stephen Hawking takes
on the big questions.
Hawking reassured the audience that these questions would soon have answers, thanks to the thriving study of cosmology. Scientists are now making use of ever-more-precise instruments and powerful telescopes to observe previously unknown aspects of the universe.
"We're getting close to answering the questions, Why are we here, and where did we come from?" he said.
It's rare that a scientist acquires rock-star status, but Hawking has done just that. He spoke to a rapt audience of about 3,000, drawing an eclectic crowd that included men in business suits, college students with dreadlocks, and children in wheelchairs who apparently suffer from the same debilitating disease as Hawking.
Looking characteristically frail, Hawking, 63, spoke through a computer-driven voice synthesizer, which he controls through an infrared blink switch. The blink switch recently replaced a hand switch, which he had become too weak too use. His muscles have continued to deteriorate from Lou Gehrig's Disease, or amyotrophic lateral sclerosis.
Time and history
Hawking is the Lucasian professor of mathematics at the University of Cambridge, a post once held by Sir Isaac Newton. He is known for his contributions to the understanding of quantum theory, black holes and the Big Bang theory of the universe's origins. Hawking is currently promoting his new book, "A Briefer History of Time," a follow-up to his best-selling work, "A Brief History of Time."
He's also known for a great sense of humor, which he displayed numerous times throughout the evening. In an introduction, the speaker illustrated his trademark wit by describing a recent interview on "Larry King Live," during which Hawking was asked what he didn't understand about the universe. He replied: "Women."
During the lecture, he referred to a conference he once attended on cosmology, in which Pope John Paul II expressed his views on the study of the universe. The Pope told the attending scientists not to inquire into how the universe began, but rather to study how it evolved. Hawking said that he was happy the Pope didn't realize he was presenting a paper on the topic at the conference because he didn't want to suffer the same fate as Galileo, who was born 300 years before Hawking.
"I didn't fancy being handed over to the Inquisition," he said.
In a show of good timing, Hawking displayed an overhead slide showing a stone prison wall with his face peering through the bars of a lone window.
Underscoring the notion that people have always questioned their origins, Hawking touched on various understandings of the world throughout the centuries. For example, he began his talk by retelling an African creation myth about God vomiting up the sun, moon, stars, animals and then, finally, man.
Hawking recounted his theory, developed with Roger Penrose, in which they showed thatimplied space and time would have a beginning in the Big Bang. That's the moment at which the universe expanded, from an extremely dense state, by a million trillion trillion times in a fraction of a second. These results showed it was necessary to join relativity with quantum theory, which Hawking called the great scientific development of the 20th century.
One consequence of the unification of quantum theory and relativity is Hawking's discovery that black holes should not be completely black but should emit radiation and eventually evaporate.
When asked which scientists had inspired him most, Hawking answered that it was Galileo for his observational powers, and Einstein for his theory of relativity. He also said that Einstein "reassuringly" has some blind spots, such as quantum mechanics and gravitational collapse.
When asked about his thoughts on President Bush's proposal to put a man on Mars within 10 years, Hawking simply replied: "Stupid."
Hawking answered one question with more seriousness than others--that concerning his feelings about the U.S. government's policy on stem-cell research.
In Britain, he said, stem-cell research is seen as a great opportunity.
"America will be left behind if it doesn't change its policy," he said.